Drosophila PIWI Interacts with Non-coding Small RNA to Regulate the Epigenetic Status of Telomeric Associated Sequences

Haifan LinDepartment of Cell Biology; Duke University Medical Center

The Drosophila piwi gene is the founding member of Piwi/Argonaute gene family that has recently been demonstrated to play a key role in the RNAi pathway. This pathway induces transcriptional gene silencing by epigenetic regulation and post-transcriptional gene silencing via sequence-specific mRNA degradation or translational repression. We previously showed that piwi is required for germline stem cell maintenance. Our recent data suggest that piwi may achieve this function by regulating the epigenetic status of its target genomic sites. We found Telomeric Associated Sequences (TAS) as one of the target genomic sites of the PIWI protein. PIWI is associated with endogenous non-coding small RNAs transcribed from the TAS. To our surprise, Chromatin IP and position effect variegation analyses indicate that PIWI is required for the maintenance of the euchromatic status of TAS. This function of PIWI appears to be opposite to its role in maintaining the heterochromatic state of centromeric regions.